Key lock systems are used to provide secure access to houses, buildings, cars and other such property. Generally, a key lock system includes a key lock and a key. The key lock generally includes a lock housing and a lock mechanism having a keyhole. The key is constructed such that it engages the keyhole and locks and unlocks the lock mechanism. Only a properly constructed key will function in a given key lock. One type of conventional key lock is a key lock having a rotating lock cylinder. In this type of key lock, a number of lock pistons are moved by a key inserted into a keyhole in the rotating lock cylinder. The correct key will position the lock pistons such that the rotating lock cylinder will rotate with the key. In this manner, the lock is locked and unlocked.
It is advantageous for some applications to provide security in addition to a mechanical match between the key and the key lock. One way to provide additional security is to construct the key lock such that the key lock can interrogate and identify whether a key is the correct key. Some of these key lock systems include a transponder in the key and an interrogation antenna and electronics in the key lock. If the key is not correct, the system may remain electrically locked even though mechanically unlocked. If the key is the correct key, the key lock can be both mechanically and electrically locked and/or unlocked.
It is a problem with key interrogation systems to activate interrogation efficiently. The interrogation electronics need to be triggered only when a key is proximate to or preferably inserted into the keyhole. One conventional method allows the interrogation electronics to run constantly, but this shortens the lifetime of any key lock system in which a battery is used. An alternate method is to use a contact switch in the keyhole. However, this generates a problem in that extra wires associated with the contact switch are required to extend from the lock mechanism. The contact switch and extra wires are subject to wear and tear and require extra modifications to conventional key lock systems.